The present invention relates to a film cassette, particularly to an X-ray film cassette, which is provided with a closable opening through which data can be exposed onto a predetermined portion of a film accommodated in an internal compartment of the cassette.
Cassettes of this type are already known and currently available on the market in a variety of constructions. In one known cassette of this type which has been disclosed in the German Patent DE-PS No. 26 46 725, the opening through which the data can be exposed on the predetermined portion of the film in the cassette is closable by means of a plate-shaped closure which is mounted on the cassette for sliding displacement between its closed position where it extends across the opening and light-tightly covers the same, and an open position where it clears the opening. In order to avoid the possibility that the closure could be accidentally displaced towards its open position during the handling of the cassette and thus would expose the predetermined portion of the film in the cassette to ambient light, a latching member is mounted on the closure and engages the housing in the closed position of the closure to hold the closure in this position until the latching member is moved by an outside influence towards its releasing position in which it is disengaged from the housing and thus permits the shifting of the closure towards its open position. The latching member is being biased towards its latching position by a biasing force which has to be overcome by the external influence before the latching member moves into its releasing position. The latching member of this cassette is contructed as a rocker which is held by a spring in its latching position in which it holds the closure in its closed position. The rocker can be displaced against the action of the spring force out of its latching position and into its releasing position by means of magnetic force acting on the rocker from the outside, so that the closure can be displaced towards its open position upon movement of the rocker into its releasing position due to the action of the external magnetic force thereon, and data can be exposed on the predetermined portion of the film accommodated in the internal compartment of the cassette through the now unobscured opening. This data exposure onto the film is performed in an exposure device which has been especially developed and constructed for this purpose and which projects the respective individual data onto the predetermined portion of the film in the cassette. To provide the data on the film, the cassette containing this film is introduced into the exposing device which is also equipped with a magnet acting on the rocker and displacing the same into its releasing position upon introduction of the cassette into the exposing device. In addition thereto, this device includes a gripping or actuating arrangement which is capable of engaging an external projection on the closure and shifts the latter from its closed position towards its open position prior to the exposure of the data on the predetermined portion of the film in the cassette but subsequent to the movement of the rocker by the magnet into the releasing position, and back again into the closed position after the termination of the exposure and prior to the withdrawal of the cassette from the exposing device.
As advantageous as this cassette may be in certain respects, it is disadvantageous in other respects. So, for instance, this cassette is rather expensive because of its quite complex construction and since the rocker must be made of a ferromagnetic material. In addition thereto, the above-discussed construction of the cassette requires the use of a specially constructed device for exposing the requisite data onto the predetermined portion of the film on the cassette, which exposing device must be equipped with a magnet. Furthermore, the actions of the magnet and of the actuating arrangement of the exposing device must be synchronized with one another, which further contributes to the high cost of use of film cassettes of this type.